This paper, by using digital image method, studied the structural development of cultivated soils under non-tillage system with simulated laboratory conditions and natural filed conditions. The obtained images qualitatively showed that aggregates in soils became larger, and soil blocks became more compacted under the states of non-tillage. The analytical results of aggregate and pore size distributions clearly showed that smaller aggregates and pores decreased while larger aggregates and pores increased. The results of field soil samples also showed that natural interval rainfall may have a function on adjustment of soil structure, yet it is still uncertain whether non-tillage system is beneficial to soil properties and agricultural production if judged from the soil images and the changes of aggregate and pore size distributions.